1. Field of the Invention
The present invention relates to a nesting method and a punching method for a machine tool control system capable of machining efficiently in a short period of time.
2. Background and Related Arts
When a plurality of parts of different sizes are to be blanked from a single material (standard length material) in sheet metal processing, nesting for allocating these parts to the material in such a manner that the proportion of a portion of the material effectively used as the parts in the whole material becomes large is automatically performed by a computer.
For instance, in a machine tool control system shown in FIG. 1, a tool center 1 reads a machining schedule prestored in a file 3 and carries out nesting processing on a prestored material when the machining schedule indicates sheet metal processing for blanking a plurality of products.
This nesting processing is described in detail. FIG. 2 is a diagram for explaining the nesting processing of the tool center 1. For instance, when it is planned to nest two products A, one product B and one product C having respective shapes shown in FIG. 2 on the same material, a nesting processing unit 15 of the tool center 1 reads a reference shape ai from which these prestored products can be blanked from a material information file 7 and plans to nest the above products on the shape ai.
For instance, two products A, one product B and one product C are to be blanked from the shape ai as shown in FIG. 2 and a machining program m1 for this blanking information S1 is created and stored in a machining program file 9.
In addition to the above products, when a product D is planned to be nested on the same material, the nesting processing unit 15 of the tool center 1 reads a shape bi from which the product D can be blanked from the material information file 7 and plans to nest the product D.
For instance, nine products D are to be blanked from this shape bi as shown in FIG. 2 and a machining program m2 for this blanking information S2 is created and stored in the machining program file 9.
As shown in FIG. 2, nesting schedules Ki based on these machining programs m1 and m2 and blanking information S1 and S2 are created. In FIG. 2, for example, a "10-th" nesting schedule Ki shows that nesting is carried out on a single material using the machining program m1 based on the blanking information S1. A "20-th" nesting schedule Ki shows that nesting is carried out on a single material using the machining program m2 based on the blanking information S2.
The tool center 1 copies the nesting schedules Ki and the machining programs mi into a controller 11.
FIG. 4 shows the configuration of an automatic warehouse 131 included in a peripheral equipment 13. The controller 11 draws the first nesting schedule Ki, compares this nesting schedule Ki with prestored inventory information Ji in the automatic warehouse 131 and judges whether the material ti of the nesting schedule Ki is present in the inventory information Ji.
This inventory information Ji, as shown in FIG. 4, stores numbers of shelves 133 (133a, 133b, 133c, . . . ) of the automatic warehouse 131, names of pallets 135 (135a, 135b, 135c, . . . ), names (including shape, size and material) of materials (material A, material B, . . . ) on the pallets 135 and the number of the materials in a corresponding manner.
When the material ti of the nesting schedule Ki is stored as inventory information Ji, a signal (to be referred to as "shelf switching instruction signal" hereinafter) for switching to a shelf storing the material corresponding to the material ti is supplied to a line control board 23. A machining program mi for the machining schedule Ki is drawn and transferred to a CNC device 25 by, for example, DNC transfer system.
The automatic warehouse 131 draws a pallet 135 on a shelf 133 specified by the shelf switching instruction signal and carries a material pi mounted on this pallet 135 to a machine tool 27, such as a turret punch press. The machine tool 27 blanks the material pi mounted on the pallet 135 based on the machining program mi specified by the nesting schedule Ki. When the machine tool 27 cannot blank the material pi mounted on the pallet 135 based on the machining program mi, it supplies a blanking error signal to the controller 11 through the line control board 23 immediately.
The controller 11 stops operation as soon as it receives the blanking error signal. That is, the conventional machine tool control system makes a blanking plan without confirmation from the tool center I that a material pi large enough to enable the products of the nesting schedule ki to be blanked therefrom is actually present in the automatic warehouse 131.
The machine tool 27 is provided with a terminal 29 for handling an urgent order or special order on the site. When an operator operates this terminal 29, the operator judges whether a material (not blanked) with which the order can be accepted is present in the automatic warehouse 131 and operates the terminal 29 to carry out nesting when the material is present on a pallet of a shelf.
When products blanked by the machine tool 27 are stored on pallets, either a nesting storage system, such as that shown in FIG. 3A, or a position specification storage system, such as that shown in FIG. 3B, is employed.
The nesting storage system shown in FIG. 3A is to arrange blanked products on a pallet 135 by reproducing a blanked image. This system has such advantages that storage efficiency is high without excess or shortage of space on the pallet 135 and products can be stored at a uniform height.
The position specification storage system shown in FIG. 3B is to pile up the same products at the same location of the pallet 135. This system is advantageous when the products are to be taken out because the same products are stored at the same location of the pallet 135.
Punching by the machine tool 27 is carried out using a single turret punch press as a punching machine. That is, a plurality of punches/dies are set on upper and lower turrets of the turret punch press and required punches/dies are searched from the plurality of punches/dies and positioned at the machining location to carry out several different types of punching on a workpiece.
As described above, since the conventional machine tool control system makes a blanking plan without the tool center's confirmation that a material large enough to enable the products of a nesting schedule to be blanked therefrom is actually present in the automatic warehouse, it has such a problem that machining takes time.
Therefore, when there is no material of a size predetermined by the tool center in the automatic warehouse, even if a machining program for blanking is created, machining based on this machining program may not be carried out.
Since the tool center does not carry out nesting for a special order, but a field operator carries out nesting by selecting a material which is not blanked, a large area remains on this material after nesting.
Further, when blanked products are stored on a pallet, either nesting storage or position specification storage system is employed. However, in either system, since the tool center causes products to be stored without taking into consideration the field conditions and schedule, there has been such a problem that a pallet has been occupied by specific products for a long time or machining takes time because a pallet must be taken in and out frequently.
Further, since machining is carried out by a single turret punch press based on a nesting schedule, there has been such a problem that machining takes time as a whole because a machining time required by the turret punch press takes long and other machine tools on a production line have to wait.